Use of electricity to inhibit macroinvertebrate grazing of epilithon in experimental treatments in flowing waters

Electricity delivered from a modified electric fence charger was used successfully to reduce grazing pressure on epilithon within experimental stream channels in the field without influencing flow through the channels. Laboratory experiments demonstrated that the presence of an electrical field similar to that used in the stream channels did not significantly influence epilithon biomass. Although more macroinvertebrates were collected from channels receiving electricity than those without, the much higher epilithon standing crop, measured as chlorophyll a (7-30X higher) and ash-free dry mass (3-5 X higher), within electrified channels suggested that animals not excluded were insignificant grazers. Taxonomic composition in stream channels without electricity was similar to the river, both with 60-70% mayflies and 7-15% Diptera. in contrast, channels with electricity had 3-25% mayflies and 60-80% Diptera. Electricity proved to be an efficient way of reducing grazing pressure on epilithon through changes in the composition of invertebrate grazers.